Come To Friday's early morning class (6:10am) to see this one in action!  I'm calling it a "band plank with row".  You may decide to call it "really hard", or maybe you have another name for it!  Here's the deal:  You get into a plank position.  Some of you may stop there--it's hard enough!  On your forearms (use extra cushioning if you need to) and your toes.  In front of you, you've attached a band to something solid, just at about mid calf level, although a bit higher will work.  Now while maintaining that plank position, you pull the band back on one side.  Do 12, then repeat on the other side.  Rest, and do 2 more sets of 12 per side.